Eukaryota: Fossil Record

The vast majority of the exhibits in this virtual museum deal with the fossil history of eukaryotes. Obviously, it is not possible to summarize the entire history of eukaryotes on one page! However, the fossil record of the earliest stages in eukaryote evolution will fit, so here goes:

Eukaryotes are defined by the presence of a nucleus. Hence there was much excitement when these microfossils were found in the 1 billion-year-old Bitter Springs Formation of northern Australia, and similar microfossils were found in even older rocks. About 5 micrometers across, these spherical fossils seem to have preserved nuclei. This interpretation is now doubted; it's more likely that the "nucleus" is the product of shrinkage of the cell contents, and these fossils could easily be cyanobacteria

More probable eukaryote fossils begin to appear at about 1.8 billion years ago. These are spherical fossils of likely algal protists, called acritarchs.